posted by Sara .
A solution of 2.50 g of a compound having the empirical formula C6H5P in 25.0 g of benzene(C6H6) is observed to freeze at 4.3 degrees C. Calculate the molar mass of the solute and its molecular formula.
I think I got the answer.
Molar Mass = 119 g/mol
Molecular formula is the same = C6H5P
I wonder how you came up with 119 g/mol?
delta T = Kf*m
5.5-4.3 = 1.2 for delta T.
I found Kf = 4.90
1.2 = 4.90*m
m = 1.2/4.90 = 0.2449
m = moles/kg solvent
moles = m*kg solvent = 0.2449*0.025 = 0.00612 moles.
moles = grams/molar mass or
molar mass = grams/moles = 2.50g/0.00612 = about 400 or so. Check my work.